Mould for forming the headpiece of deformable tubular plastic containers

A mould for forming the top of deformable tubular plastic containers comprising a tubular body (51) and a headpiece (52) of plastic material bonded to one end of the tubular body (51), the mould comprising:

• a punch (10) having an outer surface (11′) arranged to engage the container tubular body (51) as an exact fit and an end portion (13) projecting axially from tie lower end of the cylindrical outer surface 8 (11′) and
• a die (30) arranged to form, in combination with the lower surface (13′) of the punch, a cavity (F) for forming the headpiece (52) of the container, said die (30) having a concave surface (32′) arranged to receive as an exact fit, by axial penetration, the lower of the cylindrical outer surface (11′) of the punch together with the lower end of the tubular body (51) of the container,
• the headpiece (52) being formed within the forming cavity (F) and being pressure-bonded therein to the lower end of the tubular body (51),
• the punch (10)/die (30) comprising a radial deformation means (22, 20 62, 65), positioned on its outer surface (11′)/concave surface (32′) which extends annularly along the entire circumference of this surface to act on the tubular body (51) of the container, and is arranged to assume a normal position in which its outer surface does not project radially from the cylindrical outer surface (11′) of the punch/from the concave surface (32′) of the die (30), and an active position in which it is urged in a radial direction in such a manner as to press the tubular body (51) against the opposing surface of the die/punch,
• characterised in that
• said radial deformation means are positioned within an annular chamber (21, 61) which is provided in the punch (10)/die (30), is open towards the cylindrical outer surface (11′) of the punch/the concave inner surface (32′) of the die, and is in the form of a flexible annular element (22, 62) positioned to close the annular chamber (21, 61) but with its outer surface not normally projecting from the annular chamber (21, 61), said annular element (22, 62) being arranged to deform radially until it presses the tubular body (51) against the opposing surface (32′) of the die (30)/against the opposing surface (11′) of the punch, as the result of feeding pressurised fluid into the chamber (21, 61);
• said flexible annular element (22, 62) is in the form of a sleeve or elastomeric material, the section through which is relatively narrow and elongate in a longitudinal direction;
• and
• with said flexible annular element (22) there is associated a second metal sleeve (24) elastically flexible in radial direction, and interposed between the tubular body (51) and the sleeve of elastomeric material (22).